The product such as tires or conveyor belts usually uses a composite of unvulcanized rubber and steel wires as an intermediate material. The steel wires to be used in the product are required to draw themselves highly for developing their high strength. In order to improve the adhesiveness between the steel wires and the rubber and to enhance the lubricity at the drawing time, on the other hand, it is usual to plate the steel wires before drawn with brass or zinc.
Here, the brass-plated wires or the zinc-plated wires before drawn are covered on their surfaces with a thick oxide film. Especially the brass-plated wires plated by a heating diffusion method are seriously oxidized on their surfaces by the high heat at the diffusion time. In the brass-plated case, the oxides to be formed on the surfaces are mainly composed of a zinc oxide.
As the brass-plated wires or the zinc-plated wires having such thick oxide films before drawn are made thinner through multistage drawing dies, their oxide films having a poorer malleability than that of brass or zinc are preferentially scraped off so that the steel wires take the fresh brass or zinc surfaces having very little oxide film area at the stage to pass through the final drawing die.
The plated surfaces in this stage are high in chemical potentials and rich in reactivities. Therefore, the drawn steel wires react, when exposed to the air, with the oxygen in the air to form the oxide films again, and these oxide films become the thicker as the longer time elapses. On the other hand, the drawn steel wires produce zinc hydroxide or copper hydroxide, if exposed to a highly humid atmosphere containing much moisture, so that the deterioration of their surfaces further advance.
The steel wires thus plated with brass or zinc are characterized to be easily oxidized so that they are shipped, after drawn, with a drying agent in a strictly sealed state.
When the composite of the steel wires and the unvulcanized rubber is to be produced, on the other hand, It is necessary for preventing the oxidation before the rubber coating to protect the creel, on which the steel wire is wound, with corrosion-preventing paper or to make a strict temperature/humidity management on the stocking place of the creel or the creel used for the rubber coating step. Therefore, the cost for the facilities or for utilities is raised to cause a problem that the cost for producing the composite of the steel wires and the unvulcanized rubber is raised. If the stocking management is insufficient, on the other hand, the steel wires have their surfaces deteriorated to cause a problem that the adhesiveness between the steel wires and the rubber drops.
An object of the present invention is to provide a method and apparatus for producing an elastomer/steel-wire composite, which can improve the adhesiveness between the steel wires and the elastomer and can reduce the production cost.